The present invention relates to an air filter arrangement for an internal combustion engine, in particular for the two cycle engine of a manually guided implement such as a power saw, a cut-off machine, or the like.
U.S. Pat. No. 6,328,288 B1 discloses a carburetor having an air filter, with a mixture channel and an air channel opening out at the base of the air filter. U.S. Pat. No. 5,503,649 A furthermore discloses disposing shield elements between the inlet opening of the mixture channel and the filter element for retaining fuel that pulses back out of the mixture channel, thus preventing contamination of the air filter.
With air filter arrangements where an air channel and a mixture channel communicate with the clean chamber of the air filter, the channels are customarily disposed on the air filter in such a way that no fuel can pass into the air channel from the mixture channel.
It has been shown that at low speeds, a considerable portion of the fuel passes back into the air filter from the mixture channel due to the pulsations in the mixture channel. This fuel is not available for the combustion, and thereby results in a leaner mixture in the combustion chamber of the internal combustion engine. This impairs the operating behavior of the internal combustion engine.
It is an object of the present invention to provide an air filter arrangement for an internal combustion engine that also at low speeds enables a good operating behavior.